The main objective of this proposed study is the investigation of plasma membrane glycoconjugate metabolism in metastatic and nonmetastatic mammalian mammary tumors including human metastatic mammary tumor cells grown in tissue culture. Cells will be treated with neuraminidase and galactose oxidase prior to radiolabeling with (3H)-sodium borohydride (Gahmberg et al., J. Cell Biol. 68, 642, 1976). The localization and metabolic fate of this labeled cell surface material will be assessed in vitro. Internalization and reutilization of labeled cell surface material will be monitored with electron microscope autoradiography while plasma membrane shedding of this material will be quantitated by use of scintillation counting methods. Labeled cell surface material (glycoprotein and glycolipid) and shed cell surface material will be characterized by use of sodium dodecylsulfate polyacrylmide slab gel electrophoresis, paper chromatography and thin layer chromatography. The localization and shedding of ectosialytransferase of human and rat mammary tumor cells will be studied in light of the increased serum sialytransferases observed both in humans and rats, (Bernacki and Kim, Science, 195, 577, 1977) bearing metastatic mammary tumors. The rat serum sialytransferases will be further characterized and purified and their role in tumor metastasis will be investigated.